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Origin of letter drills

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  • Origin of letter drills

    Recently, someone asked me about the origin of the numbered (wire gage) drills.
    A bit of googling revealed that their sizes are based on the Stub's steel
    (note, not iron) wire gage.

    Of course, this immediately led to the question of the origin of the letter

    Are they based on some particular wire gage as the numbered are? If so, which

    Were 26 sizes selected because the alphabet has that many letters or was it
    coincidence that the sizes needed to fill the gaps totaled up to 26?

    Regards, Marv

    Home Shop Freeware - Tools for People Who Build Things
    Regards, Marv

    Home Shop Freeware - Tools for People Who Build Things

  • #2
    Well its a good ting they weren't invented in Canada. Otherwise we'd only have one size "A".

    Sorry I could not resist
    Forty plus years and I still have ten toes, ten fingers and both eyes. I must be doing something right.


    • #3
      Wouldn't that be two: an 'e' and 'h'? eh?

      Speaking of which: how long has that stereotype of Canadian speech been around?
      I only started hearing that within the last 15 or 20 years. And it seemed at the time I started hearing it, that it was kind of a new joke.
      But then, I never lived near the border, so I guess I could've just missed it.


      • #4
        Time for some history eh?
        Free software for calculating bolt circles and similar: Click Here


        • #5
          Actually I kinda like the 'eh'. Sorta spices up the sentence.

          I am tho, sick and tired of the "...he goes.." and "... I'm like..", as used in the first of that discussion on the link Evan posted.

          (...guess Marv's due an apology for sidetracking his thread. Sorry Marv.)


          • #6
            All the numbered and lettered drills are a piss poor excuse at trying to be Metric drills - want a really complete set of drills? Metric in .1mm steps!

            I am sure this abortion was the result of Americans refusing to go metric - instead opting for a Phillips screw when the Superior Canadian Robertson screw was already available - just because it was invented in Canada (can't have that or an Avro Arrow flying overhead, can we?) and is still the best screw in town...

            RANT MODE OFF
            reboot RANTING MODE

            P.S. the Bomark missle sucked and the only reason you monkeys have air superiority is because of Canadians designing your jets (re:Avro)
            (But I still love you crazy monkeys!)

            Rant Mode really off now

            [This message has been edited by Thrud (edited 02-10-2005).]


            • #7
              To put this back on track I just submitted the question to the Morse Cutting Tools "Ask the Experts" web page. They say they will get back within 24 hours.
              Free software for calculating bolt circles and similar: Click Here


              • #8
                Aahh, quit bellyaching Thrud. We like some Canadian things. For example,, ah.., well Canadian bacon is pretty good. ...and hockey. That's gotten real popular down here.


                • #9

                  And don't forget all those really hot Canadian women like K. D. Lang.

                  [This message has been edited by pgmrdan (edited 02-10-2005).]


                  • #10
                    why dont you ask BILKO


                    all the best.mark


                    • #11
                      I was told that it is just another set of drill sizes to allow for different percentage threads.Sometimes you need other than 70%.
                      I just need one more tool,just one!


                      • #12
                        I don't know the origin of letered sizes but numbered size diameters are .060" + .013 X #. For example a #10 is .060 + 10(.013) = .190" Who decided on .013????? or decided to add it to .060? This might be interesting history but all they taught us in history class in school was history of governments. I wonder if all governments in their day were considered as screwed up at the time as we consider ours screwed up now?
                        Oops - sorry to diverge.



                        • #13
                          Hey Evan, that's a hell of a good expanation why we use eh, eh?


                          • #14
                            That "eh" was in fairly common use in Minnesota when I was a kid. But they took Canadian coins without a problem back then also.

                            They hand out the coins here in Missouri, but they sure don't want them back.....but at least now that we in the US use 25 franc pieces instead of quarters, who can tell the difference? Not the droids running the registers.

                            Letter sizes don't seem to make much sense. Maybe they advance by a multiplier, but I haven't checked. And a few of them duplicate other sizes. Like A, same as a 15/64, and darn near 6mm.

                            And, since the metric system was second, it makes sense that it would be set up to avoid the peculiarities of the older systems.

                            If you think drills are weird, check out old forms of liquid measure. Drachms, Firkins, minims, hogsheads, etc.....and to think the English/Canadians came up with those odd things........

                            [This message has been edited by J Tiers (edited 02-10-2005).]

                            Keep eye on ball.
                            Hashim Khan


                            • #15
                              I recently bought a set of Chinese letter drills - there are 2,000 of them in the set...

                              All of the gear, no idea...